Generally, ethylene is a representative material of a basic raw material in a petrochemical field. In a petrochemical process, various materials are produced through various processes based on olefin compounds such as ethylene and propylene.
The olefin is obtained by cracking naphtha or is obtained from ethane. In Korea, the olefin compound such as the ethylene has been mainly produced using the naphtha as a raw material.
In a method of producing the olefin from the naphtha, conventionally, a process was performed at a high temperature of 1000° C. or more using naphtha cracking center (NCC).
Recently, a process of producing the olefin from the naphtha at a lower temperature of about 700° C. using a catalyst has been commercialized.
In a process of using the catalyst, the naphtha is supplied together with steam to a lower end of a riser and a regenerated catalyst pushed out from a catalyst regenerator is again supplied to the lower end of the riser, the naphtha and the catalyst are mixed with each other, and the olefin is produced by cracking the naphtha while allowing the naphtha to rise along the riser. The catalyst is coked while cracking the naphtha in the riser. That is, carbon to particles cover a surface of the catalyst.
The riser is connected to a cyclone provided at an upper portion of the catalyst regenerator. Therefore, a produced olefin gas is separated in the cyclone, exits from a stripper vessel, and is transmitted to a main column of a fluid catalytic cracking (FCC), and the coked catalyst is separated in the cyclone, and falls down. A fuel gas is supplied to a waste heat boiler.
In addition, the catalyst is also used in the conventional naphtha cracking center. In this case, the naphtha generates a significantly large amount of coke of about 7% of a weight of the catalyst while being cracked at a high temperature. That is, carbon particles cover a surface of the catalyst. The caked catalyst should be regenerated, be again transmitted to the riser, be mixed with the naphtha, and be used for a naphtha cracking reaction. However, when the catalyst is coked, it is difficult to smoothly generate the naphtha cracking reaction. Therefore, the coked catalyst falling to the bottom of the catalyst regenerator is regenerated. That is, the regeneration is to burn away the coke attached to the catalyst.
In the case in which an amount of used catalyst is large, the catalyst forms a fluidized bed type having a high density. That is, the catalyst is accumulated in an inner portion of a central wall provided at a lower end of a stand pipe inducing the catalyst. In order to prevent such a phenomenon, high-temperature air and stream are sprayed from a lower side of the inner portion of the center wall toward the falling catalyst, together with a fuel for regenerating the catalyst. The high-temperature air and stream spraying upward help to regenerate the catalyst and prevent a rise of a density in the catalyst fluidized bed type.
Such a catalyst regenerator is not appropriate for being applied to a catalyst regenerator in which an amount of used catalyst is small. That is, the catalyst regenerator regenerating a catalyst used in a large amount includes the stand pipe and the center wall, and requires components for supplying the high-temperature air and stream to the inner portion of the center wall.